4.4BSD/usr/src/kerberosIV/des/pcbc_encrypt.c
/*
* $Source: /afs/athena.mit.edu/astaff/project/kerberos/src/lib/des/RCS/pcbc_encrypt.c,v $
* $Author: jtkohl $
*
* Copyright 1985, 1986, 1987, 1988 by the Massachusetts Institute
* of Technology.
*
* For copying and distribution information, please see the file
* <mit-copyright.h>.
*
* These routines perform encryption and decryption using the DES
* private key algorithm, or else a subset of it-- fewer inner loops.
* ( AUTH_DES_ITER defaults to 16, may be less)
*
* Under U.S. law, this software may not be exported outside the US
* without license from the U.S. Commerce department.
*
* The key schedule is passed as an arg, as well as the cleartext or
* ciphertext. The cleartext and ciphertext should be in host order.
*
* These routines form the library interface to the des facilities.
*
* spm 8/85 MIT project athena
*/
#ifndef lint
static char rcsid_pcbc_encrypt_c[] =
"$Id: pcbc_encrypt.c,v 4.11 90/01/02 13:46:30 jtkohl Exp $";
#endif lint
#include <mit-copyright.h>
#include <stdio.h>
#include <des.h>
#include "des_internal.h"
extern int des_debug;
extern int des_debug_print();
/*
* pcbc_encrypt is an "error propagation chaining" encrypt operation
* for DES, similar to CBC, but that, on encryption, "xor"s the
* plaintext of block N with the ciphertext resulting from block N,
* then "xor"s that result with the plaintext of block N+1 prior to
* encrypting block N+1. (decryption the appropriate inverse. This
* "pcbc" mode propagates a single bit error anywhere in either the
* cleartext or ciphertext chain all the way through to the end. In
* contrast, CBC mode limits a single bit error in the ciphertext to
* affect only the current (8byte) block and the subsequent block.
*
* performs pcbc error-propagation chaining operation by xor-ing block
* N+1 with both the plaintext (block N) and the ciphertext from block
* N. Either encrypts from cleartext to ciphertext, if encrypt != 0
* or decrypts from ciphertext to cleartext, if encrypt == 0
*
* NOTE-- the output is ALWAYS an multiple of 8 bytes long. If not
* enough space was provided, your program will get trashed.
*
* For encryption, the cleartext string is null padded, at the end, to
* an integral multiple of eight bytes.
*
* For decryption, the ciphertext will be used in integral multiples
* of 8 bytes, but only the first "length" bytes returned into the
* cleartext.
*
* This is NOT a standard mode of operation.
*
*/
int
des_pcbc_encrypt(in,out,length,key,iv,encrypt)
des_cblock *in; /* >= length bytes of inputtext */
des_cblock *out; /* >= length bytes of outputtext */
register long length; /* in bytes */
int encrypt; /* 0 ==> decrypt, else encrypt */
des_key_schedule key; /* precomputed key schedule */
des_cblock *iv; /* 8 bytes of ivec */
{
register unsigned long *input = (unsigned long *) in;
register unsigned long *output = (unsigned long *) out;
register unsigned long *ivec = (unsigned long *) iv;
unsigned long i,j;
static unsigned long t_input[2];
static unsigned long t_output[2];
static unsigned char *t_in_p;
static unsigned long xor_0, xor_1;
t_in_p = (unsigned char *) t_input;
if (encrypt) {
#ifdef MUSTALIGN
if ((long) ivec & 3) {
bcopy((char *)ivec++,(char *)&xor_0,sizeof(xor_0));
bcopy((char *)ivec,(char *)&xor_1,sizeof(xor_1));
}
else
#endif
{
xor_0 = *ivec++;
xor_1 = *ivec;
}
for (i = 0; length > 0; i++, length -= 8) {
/* get input */
#ifdef MUSTALIGN
if ((long) input & 3) {
bcopy((char *)input,(char *)&t_input[0],sizeof(t_input[0]));
bcopy((char *)(input+1),(char *)&t_input[1],sizeof(t_input[1]));
}
else
#endif
{
t_input[0] = *input;
t_input[1] = *(input+1);
}
/* zero pad */
if (length < 8) {
for (j = length; j <= 7; j++)
*(t_in_p+j)= 0;
}
#ifdef DEBUG
if (des_debug)
des_debug_print("clear",length,t_input[0],t_input[1]);
#endif
/* do the xor for cbc into the temp */
t_input[0] ^= xor_0 ;
t_input[1] ^= xor_1 ;
/* encrypt */
(void) des_ecb_encrypt(t_input,t_output,key,encrypt);
/*
* We want to XOR with both the plaintext and ciphertext
* of the previous block, before we write the output, in
* case both input and output are the same space.
*/
#ifdef MUSTALIGN
if ((long) input & 3) {
bcopy((char *)input++,(char *)&xor_0,sizeof(xor_0));
xor_0 ^= t_output[0];
bcopy((char *)input++,(char *)&xor_1,sizeof(xor_1));
xor_1 ^= t_output[1];
}
else
#endif
{
xor_0 = *input++ ^ t_output[0];
xor_1 = *input++ ^ t_output[1];
}
/* copy temp output and save it for cbc */
#ifdef MUSTALIGN
if ((long) output & 3) {
bcopy((char *)&t_output[0],(char *)output++,
sizeof(t_output[0]));
bcopy((char *)&t_output[1],(char *)output++,
sizeof(t_output[1]));
}
else
#endif
{
*output++ = t_output[0];
*output++ = t_output[1];
}
#ifdef DEBUG
if (des_debug) {
des_debug_print("xor'ed",i,t_input[0],t_input[1]);
des_debug_print("cipher",i,t_output[0],t_output[1]);
}
#endif
}
t_output[0] = 0;
t_output[1] = 0;
xor_0 = 0;
xor_1 = 0;
return 0;
}
else {
/* decrypt */
#ifdef MUSTALIGN
if ((long) ivec & 3) {
bcopy((char *)ivec++,(char *)&xor_0,sizeof(xor_0));
bcopy((char *)ivec,(char *)&xor_1,sizeof(xor_1));
}
else
#endif
{
xor_0 = *ivec++;
xor_1 = *ivec;
}
for (i = 0; length > 0; i++, length -= 8) {
/* get input */
#ifdef MUSTALIGN
if ((long) input & 3) {
bcopy((char *)input++,(char *)&t_input[0],sizeof(t_input[0]));
bcopy((char *)input++,(char *)&t_input[1],sizeof(t_input[1]));
}
else
#endif
{
t_input[0] = *input++;
t_input[1] = *input++;
}
/* no padding for decrypt */
#ifdef DEBUG
if (des_debug)
des_debug_print("cipher",i,t_input[0],t_input[1]);
#else
#ifdef lint
i = i;
#endif
#endif
/* encrypt */
(void) des_ecb_encrypt(t_input,t_output,key,encrypt);
#ifdef DEBUG
if (des_debug)
des_debug_print("out pre xor",i,t_output[0],t_output[1]);
#endif
/* do the xor for cbc into the output */
t_output[0] ^= xor_0 ;
t_output[1] ^= xor_1 ;
/* copy temp output */
#ifdef MUSTALIGN
if ((long) output & 3) {
bcopy((char *)&t_output[0],(char *)output++,
sizeof(t_output[0]));
bcopy((char *)&t_output[1],(char *)output++,
sizeof(t_output[1]));
}
else
#endif
{
*output++ = t_output[0];
*output++ = t_output[1];
}
/* save xor value for next round */
xor_0 = t_output[0] ^ t_input[0];
xor_1 = t_output[1] ^ t_input[1];
#ifdef DEBUG
if (des_debug)
des_debug_print("clear",i,t_output[0],t_output[1]);
#endif
}
return 0;
}
}